Transmission system regulation



TRANSMISSION SYSTEM REGULATION .sueswvc: HAVING suasmwcss HAVING NEGATIVE TEMPERATURE NEGATIVE TEMPERATURE COEFFICIENT or RA's/smvc: COEFFICIENTS F RESISMNCE F/G. 5 03*; as o/ws FIG 6 or-sta OHMS ATTENUATION 0F GOMPENSATED NO./9 GAUGE CABLE PAIR COMPENSA TED AND NON- ATTENUAT/ON VARIATION OF NO. I9 GAUGE CABLE PAIR FROM 0'/-' 7'0 IEO'F DEC/EELS PER MILE PER IF DEC/EELS PER MILE C OHPE NSA TED 0 FREOUENCY- KC FREQUENCY KC /N l/E' N TOR R. K BULL lNG TON ATTOR EV Aug. 17, 1943.

OHMS

R. K. BULLINGTON Filed Sept. 9, 1941 RES/S TA NCE cmmcrm/s'r/cs or NETWORK or TYPE sHow/v #4 Fla. 3

- 80 40 FREQUENCY KC NON-COMPENSATED AT TENUAT ION WRlAT/O/V F NO./.9 GAUGE CABLE BUR FROM 0) T0 [F (.OMPENSA TED I I I I F RE OUE NC Y-KC 3 Sheets-Sheet 2 ATTENUA won or cou mursn AND NON- cou msnrso N0.l.9 040a: cnau: 42 PAIR use m i '3 as E o a m 20 so 40 so so mzaumcr-xc lass/smut;

CHARACTERISTICS or NETWORK Q or rm: .suomv INF/6.4

| 1 1 l l r I a 0 I0 20 30 40 50 6 0 3 Sheets-Sheet 3 so 40 5a rRsousmr xc PAIR VARIATION IN ATTENUATION mm TEMPERATURE 9 OHMF-O'F zsouus-o'r IVON- COMPEN-S'A TED Sept R. K. BULLINGTON TRANSMIS S ION SYSTEM REGULATION Fi led ATTENUAT/ON -,vo./9 mus:

can: BUR -mm NETWORKS or TYPE snow/v In FIG. 4

COMPENSATED FREQUENCY KC FIG. I?

IVON-COMPENSATED PAIR VARIATION IN ATTENUA no/v mm TEMPER/i TURE No.19 040a: c401; PAIR ar f 120 F Aug. 17, 1943.

FIG. /4

win/01v 11v ATTENUA 110 WITH TEMPERATURE FRsouavcr-kc IN N TOR By R. K. BULL/N6 TON Ni QUE v JUNE-Q FIG. /5

FREQUENCF- KC A TTO NE)" Patented Aug. 17,1943 -41;

, amaze f," 1;. raanswnssronsrsrnrr REe LA'rroNQ" RobertK. Burlingt n, Forest nns; N, Y; assignor to Bell Telephone Laboratories, Incorporated, New 1 o YorlnN. Y., 'acorporationef New Application September 9, 1941, S nai hlo. 4110,125 6 Claims. anaan) f Thisinvention relates to electric wave systems and, more particularly, to'transmission lines and means for compensating for variations in-attenuation and impedance thereof' with temperature variations;

' An objector the invention is'to reduce theat tenuation variation with temperature of a transmission path or line,

A furtherobjectis to reduce thelinipedance variation with temperature of a transmission path or'line; f

The'transmission line may comprise a pair of telephone conductors or 'wires of the so-called open-wire type or may included in a cable .to-'

ether'with, a: plurality of other telephone pairsl The line may belofthe non-loaded type and be intended to transmit a band of frequencies, for

7 example, between 10 and 60 kilocycles per second. The ordinary telephone pair has a positive varia-' tion of resistance with temperature over the limited range embraced byatmospheric temperature; Line'i'mpedancevariations with temperature in the above-noted frequency range are normally determined by the highest frequency being trans mitt'ed, compensator units or impedancewinet works comprising one: orm ore tempe'ratureada pendent resistance "elements and a capacitive reactance element; In one embodiment, the net-. work-'may compris'e' a temperature-dependent resistance element having: 'a' negative temperature small. The changes in attenuation and impedance' with temperature are due} generally to changes in the effective highirequency resistanoe of the telephone pair, but variationsi'n induct ance, capacitance and leakance are contributing factors. Y

A feature of the invention comprises associat ing an impedance net work with a transmissionlinewhose attenuation andimpedance characteristic varies'with variation in temperaturefwhich network has a resistance component that -de'- creases substantially linearly :with frequency, a negativereactance component that increases inxa ne ative direction substantially linearly with 'frequency, and in which both components decrease substantially linearly with temperature; I

Another feature of 'the invention ("comprises compensating :for attenuation andzimpedance coeffieient ofresist'ance with a series-connected resistance and capacityin shunt therewithn In another embodiment-the'compensator unit may comprise a plurality; of impedance networks, for example, twoaone ofwhichcomprises a:networkincluding a temperature-dependent resistanca'a shunt resistance of. low temperatureicoefiicient andacapacity, and the otherofzwhich comprises a temperature-dependent resistance elementhaving a negative. temperature coefficient ofresist ance with a resistance element connected inshunt therewith. In: each instance, the shunt resistance element is preferably of low "temperature co,-

efficient: of resistance. Initheimore -elaborate I unit, the two temperature-dependent resistance elements, may be ehosen.so.as ,to be of difierent I: resistances; at the various temperatures in the range .ofrtemperatums involved.

A more" complete understanding' of this int/en tion will be obtained from the detailed description that follows hereinafter, read with referenceto theappendeddrawings, whereinzr;

. Fig. l shows a transmission path or linehaving compensator units inserted therein at spacediin tervals to compensate forattenuation and imped-j Fig-"3 shows 'aicom'pensator unit or network in 3 anc'e variations inthe line with temperature,

Fig. 2 shows a compensator unit or' ne twork heretofore proposed for use in'the arrangement of Fig. 1;

. accordance with this invention;

change withftemperatu're in atransmission line by inserting one ormor impedance networks at spaced, intervals I in the time; the network com'-; prising a. temperature-dependent:resistance:ele-

ment: and a capacitive reactance element. :Still. another feature comprises inserting one or more compensating .nnits: or networks in a transmission line to compensate for attenuation and impedance changestherein'with temperature and in which each unitincludes a plurality of;

temperature-dependent:resistance elementas ".1

In accordance? with the inventionpatra'nsmis sion. line adapted for transmitting abroad-band of frequencies has inserted therein-at. intervals i Fig 4 shows'still another compensator unit or network in accordance withthis invention; QgFigs. 5 and 6 show attenuation and attenuation variation versus. irequency; characteristic. curves for ano'necompensated cable telephonev pair, and

the same, telephone .pairfwith. compensator units 1 ofthe trpe showninjia'z insertedthereinj Fig- Tshows-resistance andneact anc versus frequenc'y characteristic curves for a thermistor compensator unitofthe typeshown in-Fi g.' 3;

Figs. 8an'd9flshow attenuation and attenuation variation: versus frequency characteristic curves' I for a. nonecompensated cable telephone pair, and

the same telephone pair with compensator units of the type shown inFig. .3 inserted therein 'Fig.;.10 ShQWs resistance: and .;,reactance,versus 2,326,826 works will depart slightly fromthe onc -shown, I

but s'u'ch deviation is not important in compari son'with the change in the 0 F. characteristic.

-The decibel per 'mile per 120 F. characteristic 7 for each" of these'cases; and forthe non-compensated telephone pair, are shown in Fig. 6.

In orderto reduce this-variation in loss with temperature, it is desirable to add one or more reactive elements so that the characteristic of the compensating unit or network will vary with frequency as well as with temperature. Networks so modified are shown in Figs. 3 and 4 of which more detailed treatment willbe gi-ven' hereinafter. Withreference to'Fig. 2,- it-willbe evident that the reactive el'ements may be included in the network'in one or thefollowing-ways: (1;) in

series with the temperature-dependent resistance 7 T; (2) in series with the resistance Rs connected in shunt with the temperature-dependent re-- sistance; (3) in parallel with boththe resistances and (4) in series-with both of the resistancesp, 1 Each of. these arrangements has advantages and limitations, but, at this time, 'it' is believed that'the arrangement of Fig.3, in WhlQIL afC'OII- denser C is connected in serieswith the resistance shunting the temperature dependent resistance,

is one of the more satisfactory of'the' possible units or networks incorporating an additional element. With the arrangement-oi Fig.i3,-the presence-0f theycondenser results in a decreasing .resistance characteristic-'with increasing frequency, as is shown desirable by TableI, and the highest reactive component will beat the low frequencies and low temperatures. Thej effectof inserting a compensating network of the't p'e shown in Fig. 3 ma 19 gauge cable telephone pair every 3,000 feet, with the network compris 'ing a-temperature-dependent resistance of. 20.6

ohms at 0 F. (4.2- ohms at 120 F.),' a shunting resistance of 13.8 ohms at 0 F; (1 7.4 ohms at 120 F.), anda 1.2 microfarad condensen'is'im' dicated by Fig. 8, the curves of which showthe characteristics of sucha. telephone pair." The] .decibels per mile per120 F characteriisticsforthe compensated andnon-compensated telephone pair are shown by Fig. 9. The characteristic for material comprising oxides of nickel; manganese .and cobalt, 'for example, as disclosed in'E. F. Dearborn application SerialNo. 280,692, filed J um 23, 1939, for Resistance materials and-method.ofmaking same," now Patent No. 2,274,592, dated Feb. 24, 19 42, is employed, the maximum a'ttenu' 1 ation per milemay be increased somewhat; The 4 use of -a silver sulphide resistance element for the temperature-dependent resistance would in-. crease the maximum attenuationiby a smaller 1 amount,"-but would not carry direct current satis-' ractorily and would beless stable. 'Another material that could be'usedfor the temperaturef dependent resistance is a composition of oxides of nickel, manganese and .coppemisuchlas is 'discation Serial No. 336,734, filed May 23,1940, for Resistance composition andmethod of making it. 7

' The desired result, of course, is to straighten the decibels per mile per-12m n. characteristic, along the zero axis. {The addition of a second reactive element to thenetwor would be'aQst-ep in this direction as [it 'wouldresult'inathe provi- Q i sion of compensation at any three frequencies, that is; the pure resistance unit or: network com pensa't es at --one frequency, "andtheunitwith a condenser compensates at two frequencies. If a second reactive 'elementis added to'the come pens'ating unit, care must be linearity with temperature?- ill 7 'Ic recapitulate at thispoint thgl iora single 'reactive element incon'junction with the compensating unit or networkof the 'type shown in Fig. 2, that is, 'to give' the network arrange;

ment of Fig; 3,*would provide compensationat" at leasttwo frequencies'inthe carrier frequency network would appear .to be one who seresistance and reactance characteristics vary linearly with frequency as well as temperature. More specifi+ cally, the attenuation -variations with tempera the compensated;line-indicates that,'in a 100 mile section; the maximum variation in thelfre quency range .of abouti12 kilocycles to-60'kilocycles is'approximately' $2.5 decibels, "with the variation below 16 kilocycles in the opposite direction to the .variaticn:above 16 'kilocycles. The resistance and reactance characteristics for the compensating unit for 0' F.,"57 Rand 120 F. conditions are shown in Fig. '7; v 1

It will be noted that the effect ofthe compensating unit on the decibels'per mile per 120 F. characteristic. is to reduce its magnitude byapproximately the same amount at all frequencies. In other words, the compensating unit under consideration would provide essentially fiat gain regulation. It'willbenoted, also; that"the.primary effect of aresistance change in the compensating uniti is. a translation of the decibelsper mile per 120.. F. characteristic with respect'to ture of. a IQ-gaugecablepair at allirequencies in the. range of lOto 60 kilo'cyclcs, maybe com ,p'ensated with suincient accuracy from apracti cal standpoin't if the compensating network has. the following general characteristics; '(1) a re-' sistance component decreasing linearly with free cuency; (2) a negativ reactance component increasing in a n ative direction linearly with fre the vertical a'xis,whilethe primary efiectfof the V additionof the condenser is a counter-clockwise I rotation of thi characteristic. iififhusccmplete compensation at anyone frequency and the'slope of the residual twistvariation (residualvariation at 60 kilocycles compared ito the residual variation at 10 kilocycles) .can'be controlled-but the shape of the-decibels per mile peri120 F; char acteristic remains essentially the same. a r

. If, a temperature-dependent resistance of a:

- The first temperature-dependent Iresistance: 1 i

jquency; and (3-) both components decreasing linearly with temperature.

When only one temperature-dependent resistance is included the compensating network.

the optimum characteristics are-obtainable only by using a' large number (if other resistance and reactive elements? in the compensating unit or network. The inventor has'det'ermined, however,

that a simpleapproximation'of the optimum net:

work is obtainable with the; network or. unit shownin Fig. 4, in which two. ..temperature{de- I 'pendentresistances T1,. Tzare. includedjone off a the temperature-dependent resistances Ti having a esistanceoft' 10W temperature iefficient:Rsi andwa condenser C1= each connected in shunt- I 1 therewithrandsthe other. temperatureedependent resistance .Tz' having aresistance Rsz. of: low tern perature coemci'ent-connected in shunt with isfpreferably of lowiresistance, andgis shunted by-the resistance Rsi to" provid japproximate taxerito avoid nontance C1 to obtain a decreasing resistance char.- acteri'stio and .an. increasing negative reactance characteristic with frequency. .The secondtem- "perature dependent resistance is of higher resistance than the first, that is, over the tempera-- ture range involved. The. two temperaturesdee pendent resistances maybe of the same material and of difierent sizes, 01' of difierent materials, of the same or different sizes, to give the resistance valuesdesired in theparticular situation.

By. using the two temperatureedependent resistances, the'major portion'of; the desired change can be obtained withtemperature-dependentresistance Trend its associated shunt resistance, the characteristics of whichare, of cour se,;con

. n ty with temperature, .andby the capaci- I stant with frequency and can be madeapproxiarensmalLf Thecharacteristics ofa typical network of the type shownin Fig. 4: are-shown n Fig. for.0 F., 57 F. and 120-F Although shownby the curves of Fig, 7 linearity especialiy at the upper frequencies; these departures arein. the opposite direction sojar as ,the effect on attenuation i concerned and ice network, the combined rcsistance elements a dependent. resistance 1 .T2 and the resistance; RS2

*A better appreciation ,cr'thc possibilities 'presented by thenetwork :of Big. '4,- is obtainable by considering the effect of varying 'ini-turn each of its various parameters. course, that, when the resistivity of the temperature-dependent resistance is changed to anothervalue, the shuntingresistancc, is also changed so that the approximate linear characteristic with temperature is retained. The curves of Figs. .13, 14 and 15were obtained with .a network in which, initially, he condenser C1 had a capacity of 1A microfarads, the tempcrature dependent resistance R1 combined. With the. 1esistance RS1 had a resistance of 218 'ohmsat 0 F. and auresistanceof 1.1 ohms at 12091. and the temperature-dependent resistance T2 combined with the resistance RS2 had a resistance of 8.2 ohms a0. F. and of 3.3 ohms at 120 F; :Ifthe constants of the network remain unchanged except that 5 combination -,of the temperatui-'e- ..is changed to one whoseresistance at 0 F; is 9 7 i I tion whose-0 Fpresistancexis equal to 2ohms. are more or less self-compensating. In thistypof T1 and RS1 was of the order of 2,.8 ohms at 0F. and of 1.1 ohmsat 120 R; thecombined g resistance of elements T2 and RS2 was of the order 0! 8.2 ohms at 0 F. and of; 3.3 ohm at 120 F.; and the capacity G1 was of the order 011.4 microfarads. r

As an example, by inserting the network of Rig-14, having thecharacteristics shown by the curve of Fig. 10, ina 19 gauge cable telephone pairat 3,000 foot intervals, the values of attennation shown in thejollowing Table II are obt me r -,-'TAB1 .E-II

Attenuat n decibels per mile 0119 gauge cable telephone pair Frcqueucykc. per sec.. 10 i0 TEL.. PAIR. COMPENSATED The attenuation for anon-compensated telephone pair is also listed. These data are plotted in .11.. The characteristic impedance of the line such a network at 3,000 foot intervals and the variations inimpedance with temperatur are reduced. For aspacing, of one mile or more, there would be less than two compensating net'- works. per wave-length, and the'resulting impede ancev characteristicjwould not be as favorable;

AT 3,000 FOOT INTERYALS resistance Ti-and the resistance .Rsiis indicated by, the curves. of Fig-14; for a combination .whose resistance at 0 F. is 3.5 ohms and for a combina- Whenthee-compensating network .is (the same as that for 'thecurvessof :Figs. 1-0,".11 and,12,"b'ut thec'apacity of the condenserjC1 is changed to onemicrofarador to two microfarads, the effect of such change is indicated by the curves of Fig. 15. Itis apparent, therefore, that by appropriate choice. of theseparametera-any expected cable telephone-pair characteristicflcan be compensated withv considerable accuracyi a Althouglrthis invention. has been disclosed with referenceto several specific'ernbodiments, it is to be understood that itis not limitedith'ereclaimsr' I V 5 What is claimed is:

I '1', A transmission'linewhosei and impedance characteristics vary with "temperature, and means inserted in'said lineito'com-. pensate forsaid variations;.said=means compris in: a plurality-of networks spacedgat-regular in tervals'in said'line, each of said networks com prising two resistances iniseries in said line and having 5 negative temperature fcoefiici'ents ofrresistance, shunted by resistances of small-temper with one of said last mentioned resistances.

. is not changed appreciably by the addition of V -2. In combination, a transmission-line .wh'o'sc attenuation and impedance characteristics vary with temperature, and means.insertedxin'said line to compensate for said-variations, said means comprising'a compensator unit includingia pair of series-connected impedance networks, each network 1 comprising a temperature-dependent resistance, a; series-connected resistance of small temperature *coefficient of resistance .and- "a capacitanceheing connected'in shunt with one of said temperatureedependent resistancesfisa'nd Ha resistance of small, temperaturecoefiicient"of The decibels-per mile per F. characteristic I for thenon-compensated and compensated tele' v hone pairsis shown by the curves of Fig. 12.

resistance being connected in" shunt withth'e sec- 0nd of said temperature dependent resistances. 53. A transmission line whose attenuation" and impedance characteristics vary with temper ature, and .means' inserted in. said line to compensatefor' said variatiomsaid meanscompris- It iissto be assumed, of

ing a compensator unit including a pair of seriesconnected impedance networks, each network comprising a resistance having a high temperaturecoefiicient of resistance, each of said networks including a resistance of small temperature coefiicient of resistance and one of the networks including 'a reactance element, saidline and said unit being subjected to the same variation in temperature but varying in resistance in opposite directions for a given temperature change. g V

4. In combination, a transmission line that varies in attenuation and impedance with temperature and means inserted in said line to com-; pensate for such variations, said line and said means being subjected to the same range of temperatures, said means comprising an impedance network having a resistance component that decreases substantially linearly with frequency and a negative reactance component that increases in a negative direction substantially linearly with frequency, both components decreasing substantially linearly with temperature,-the impedance network comprising two resistance elements having negative temperature coefiicients of resistance, each of said elements being shunted by an individual resistance of low temperature co-i efiicient of resistance, and one element being shunted by a capacitance. V i r 5. In combination, a transmission line to be subjected to a wide range of atmospheric temperatures and to transmita broad band of high frequency currents, said line being of a material havinga positive temperature coefficient of resistance and increasing in resistance with ris ing frequency, and impedance units to compensate for variation in'line resistancewith vari'a- -tion in temperature and frequency, said units being inserted in series in said line at intervals and subjected; to the same variation in-te'mper ature" and frequency as the line,,each unit com- 7 I prising a pair of resistance networks changing in resistance in a direction opposite to that of the temperature change, one network including re-; actance' means contributing a decreasing resistance and an increasing negative reactance-char} acteristic with frequency to the unit.

- The combination of claim 5 in whichone} of said networks is of higher resistance'over the temperature range than the other and'provides the major portion of the compensation for reisistance change change. 1 V ROBERT K. 'BULLINGTO-N. I

m the line with temperature 

